[Photos] Micro Switch 122ST13S-25E-J

Recently I acquired this interesting vintage Micro Switch rubber dome keyboard in NOS condition. It came with the original packaging foam but without any documentation or the original carton.

It can use AT protocol and is thus easily usable, but some keys including nav cluster and arrow keys send strange scancodes which have no use. Luckily every key has an individual scancode, making it easy to remap with Soarers converter or similar.

It is a high quality rubber dome keyboard which has some interesting characteristics, such as discrete domes plate mounted on steel, NKRO and actuation before bottoming out. The keyboard weighs about 2.1kg without cable, making it rather heavy for a rubber dome.

According to an official brochure it uses capacitive sensing, which seems odd at first because the keyboard still also uses a membrane.

The key caps are also quite nice, using medium thick dyesub PBT, some with blue sublegends. However the spacebar evidently uses ABS, and is quite yellowed even thogh the keyboard appears to be unused.

The keyfeel is pretty good, very smooth with a medium sized tactile bump at the start of the travel, afterwards the force required to press the key rises rather steeply, making it hard to bottom out; perhaps similar to mx clear.

Furthermore, the keyboard is very quiet by itself, quiter than all rubber domes I have tried before. Also there is absolutely no stabiliser rattle which along with the heavy metal mounting plate makes it a very solidly feeling keyboard.

I need some help turning off the integrated beeper without desoldering it, so if anyone has a manual to this please tell me! I tried many key combinations with the "Click" key shown in the pictures, but sadly without success.

Pictures:
Spoiler:
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Somewhat yellowed spacebar


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Thick coiled cable and a back flap for optional DIP switches? (it was empty behind it here)


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Blue caps 1


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Blue caps 2


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Backside showing the odd 2 settings flip out feet, also a date of 28th week of 1987


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Odd foot closeup


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Bottom case inside


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Top case inside


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Brass screw inserts in top case


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Keyboard assembly sitting in case, it is just clamped between the case halfs



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Slider and underside of keycap. Can also see the membrane beneath, as well as small part of rubber dome below the slider


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Back of keyboard assembly, the membrane is held within a sandwich vaguely similar to the ones in IBM model F


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Another sticker, can also see the twisted metal tabs holding the plates together


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Closeup of another twisted metal tab


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View of the controller PCB showing ribbon cables


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Another angle


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Underside of the controller PCB


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Looking into the sandwich from parallel to the plate


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From the oppsoing side of the board, showing cable plug


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From the original side, showing stabilisers

Whole imgur album: https://imgur.com/a/Qbkd9
Noobmaen
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Unread post28 Feb 2018, 00:16

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One of the PC Magazine keyboard reviews that I read (February 1992 or December 1989) mentioned the idea of capacitive membrane sensing, but said that no keyboards that they reviewed used it. Unfortunately they did not say which companies actually used it.

The awkward part is not being able to see the whole membrane. From what I can see, the lower membrane does not use dual pads like you'd find on a PCB. HaaTa or Chyros may be able to advise on the implications of the membrane that we can see there on capacitive sensing.
Daniel Beardsmore
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Unread post28 Feb 2018, 08:54

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I no longer have a place here.
Noobmaen wrote:I need some help turning off the integrated beeper without desoldering it, so if anyone has a manual to this please tell me![/size] I tried many key combinations with the "Click" key shown in the pictures, but sadly without success.

Maybe Alt-Esc ?

Also, you're invited to add (better) pictures to wiki/Micro_Switch_122ST13S-25E.
tactica
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Unread post28 Feb 2018, 10:16

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Added some new pictures to the wiki article. I still wonder how the sensing works, having NKRO using a membrane, but taking the sandwich apart requires twisting metal tabs, which I am not sure will be easy to reverse. According to this the IBM 73x3832 also supports NKRO, of which there are already full pictures of the membrane. I assume they use the same sensing method.
Noobmaen
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Unread post28 Feb 2018, 13:55

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Nice job.

A close-up of the membranes would be nice, too (through one of the holes where there is no key) — you can see them in the existing pictures, but having a dedicated photo would be easy to pick out in the image gallery.
Daniel Beardsmore
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Unread post28 Feb 2018, 18:33

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Daniel Beardsmore wrote:Nice job.

A close-up of the membranes would be nice, too (through one of the holes where there is no key) — you can see them in the existing pictures, but having a dedicated photo would be easy to pick out in the image gallery.

Look here: wiki/IBM_73x3832_Quiet_Touch This one was put in a while back and it is a pain to take these apart :)
snuci
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Unread post28 Feb 2018, 19:42

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An image for his keyboard is still very useful — we can never assume that any two keyboards are the same.
Daniel Beardsmore
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Unread post28 Feb 2018, 21:38

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